Pivoting optical device

ABSTRACT

Pivoting optical device comprising a first part ( 15 ) and a second part ( 17 ) with optical means which is pivotally movable relative to the first part about a first pivot axis ( 19 ), said optical means defining an optical laser beam path ( 21 ) in the general longitudinal direction of the second part, and further comprising bearing means ( 23 ) comprising the first pivot axis and a point laser source ( 25 ) fixedly connected to the first part for providing a laser beam in the general direction of said second part. According to the invention, the laser source is located in said optical laser beam path in the general longitudinal direction of the second part, and the bearing means present an open center region ( 29 ) so that a laser beam is allowed to pass from the laser source to the second pivotally movable part.

The invention relates to a pivoting optical device of the type definedin the preamble of claim 1.

Pivoting optical devices of this kind may be used, for example, to scana surface of a substrate with an optical probe in a direction generallyparallel to the substrate surface and in a direction perpendicular tothe substrate surface. Optical devices of the kind referred to above arealso used, for example, in optical disc apparatus to read and possiblyrecord information from/into an optical disc, but could also be usedwith barcode readers, measuring equipment, etc.

Japanese document JP-2001 357 547 A discloses a pivoting optical deviceof the kind referred to above for scanning optical discs. The devicecomprises a swing arm which is pivotally movable about a swing axis nearone of its ends, an optical focusing unit being provided at the oppositefree end. The optical focusing unit comprises optical lens means whichare axially movable relative to the swing arm structure so as to providea focusing function. Optical elements are located in the swing arm,providing an optical path from a semiconductor laser diode to theoptical focusing unit and back to an optical sensing device.

According to the cited JP document, the laser diode may be provided inthe swing arm itself near the swing axis. As an alternative, it may beprovided in a separate stationary structure apart from the swing armitself. The preamble of claim 1 therein refers to the latter kind ofsolution. In the cited Japanese document, said separate structure islocated over the pivoting end of the swing arm, and the laser diode ispositioned such that the laser beam emitted from the laser diode isdirected along the swing axis, a reflecting optical deflection elementbeing provided in the swing arm to deflect the laser beam in thedirection of the optical focusing unit at the free end of the swing arm.

Providing the diode laser in the swing arm itself presents the obviousdisadvantages of an increased swing arm mass, not only of the diodelaser proper but also of its mount and the unavoidable connecting leads.A major problem is also the heat generated by the laser diode. In somecases, such as in swing arm devices for optical disc drives, providingsufficient cooling of the pivotable moving second part may beimpossible, which will ultimately lead to the destruction of the laserdiode. Even if sufficient cooling is provided, the resulting thermalload has a negative impact on the geometrical stability of the swing armstructure as a whole and the relative positions of the optical elementspresent in the swing arm.

Providing the diode laser as a separate stationary unit in accordancewith the cited Japanese document increases the overall axial dimensionsof the optical swing arm arrangement. The optical deflection elementwhich is needed still adds to the mass of the swing arm. The means formoving the optical focusing elements of the optical focusing unit alsoincrease the movable mass of the swing arm.

The problems of the prior art indicated above interfere with the everongoing trend towards miniaturization which can be observed in theindustry and more particularly in the areas of information technologyand communication technology.

It is therefore an object of the invention to provide a novel and usefuloptical device of the kind described in the introduction which is highlysuitable for miniaturization and needs fewer optical elements bycombining the features defined in claim 1. In this way the overall axialdimensions of the optical unit are reduced. The optical deflectionelement discussed above is not needed.

The invention may be advantageously used in a pivotal optical deviceaccording to claim 2. This embodiment is characteristic of theversatility of the invention, which may be used in optical devices of amore complicated nature exhibiting combined pivotal movements.

A preferred embodiment of the invention is defined in claim 3. Bearingmeans of the gimbal type are highly suitable for the optical device ofthe invention. The intermediate part may provide an open central part ofdimensions which may be conveniently matched to the dimensions of thelaser diode and its mount, without impacting on the dimensions of thesecond pivotally movable part of the pivoting optical device.

An embodiment of the invention is preferred in accordance with claim 4.Many semiconductor lasers, if not most, exhibit a far field of generallyoblong shape, due to the physical nature of the semiconductor elementemitting the laser beam. As an example, reference is made to aspecification sheet regarding the NDHV310AA high-power violet laserdiode available from Nichia Europe B.V., a company with offices inAmsterdam, The Netherlands, exhibiting a dimensional ratio between theminor axis and the major axis of approximately 1:3. Many pivotingoptical devices which pivot in two mutually perpendicular directions doso with a larger amplitude in one direction and with a smaller amplitudein the other direction. The generally oblong nature of the far fieldpattern of the semiconductor diode laser, in many cases regarded as anunfortunate characteristic, may be completely compatible with theoperation of the optical device according to the invention owing to ajudicious orientation of the far field pattern relative to the first andsecond pivoting axes of the device.

A further embodiment of the invention is defined in claim 5, where thecollimating lens, used to collimate the laser beam and often present inoptical devices of the kind wherein the invention may be used, isstrategically placed relative to the laser source so that no room iswasted. If the laser source exhibits a generally oblong far fieldpattern, an embodiment may be used in accordance with claim 6 so as toensure that the collimator lens is always within the far field patternof the laser beam.

A highly practical embodiment of the invention is defined in claim 7. Aswing arm device having a rigid swing arm structure which may pivot intwo mutually orthogonal directions is described in Applicant's copendingpatent application filing nr. 0278881.6, filed on 19 Sep. 2002 but notpublished prior to the priority date of the present application, thecontents of which are incorporated herein by reference.

The objects and features of the invention will become more apparent fromthe following non-limiting description of a preferred embodiment givenwith reference to the accompanying drawings, in which:

FIG. 1 is a schematic perspective fragmentary view of a pivotal opticaldevice in the form of a swing arm device for use in an optical discdrive according to the invention,

FIG. 2 is a fragmentary side elevation view in cross-section,illustrating a detail of FIG. 1 on an enlarged scale,

FIG. 3 is a diagram showing in plan view the relation of the dimensionsof a collimator lens of the optical disc drive of FIG. 1 to a laserdiode far field pattern in which the collimator lens moves,

FIG. 4 is a fragmentary perspective detailed view of parts of analternative embodiment of the device of FIG. 1, and

FIG. 5 is a view similar to FIG. 3 of an alternative embodiment of theinvention.

The drawings are of a schematic nature and intended for illustrationpurposes only. The details in the Figures are drawn to an arbitraryscale which may be different from the overall scale. The same componentsare indicated by the same reference number throughout the Figures.Components and assemblies which may be configured according toprinciples which are basically known from the prior art will not bediscussed in detail.

Referring to FIG. 1, a pivoting optical device is shown in the form ofan optical disc drive of a general design disclosed in Applicant'scopending patent application, filing nr. 02078880.8 filed on 19 Sep.2002 but not published prior to the priority date of the presentapplication and incorporated herein by reference. The optical disc driveof FIG. 1 comprises a base plate 1 supporting a spindle motor 3 forrotating an optical disc 5 about a spindle axis 7, the optical disc 5comprising an information surface 9 at its lower side. A peripheralouter surface 11 of the spindle motor 3 has a pivoting optical device 13attached to it, spaced from the base plate 1. It comprises a first partgenerally denoted by the reference number 15 and a second part generallydenoted by the reference number 17 with optical means and pivotallymovable relative to the first part 15 about a first pivot axis 19, saidoptical means defining an optical laser beam path 21, the generaldirection of which is symbolically indicated by a dash-dot line andextends in the general longitudinal direction of the second element 17.Bearing means, generally denoted by the reference number 23, areprovided comprising the first pivot axis 19 as well as a point lasersource 25 fixedly connected to the first part 15 for providing a laserbeam 27 (see FIG. 2) in the general direction of said second part 17.

The laser source 25 is located on said optical laser beam path 21 in thegeneral longitudinal direction of the second part 17, and the bearingmeans 23 presents an open center region 29 so as to allow the laser beam27 to pass from the laser source 25 to the second pivotally movable part17.

The second part 17 is also pivotally movable relative to the first part15 about a second pivot axis 31 substantially orthogonally intersectingthe first pivot axis 19 at a point of intersection P, the laser source25 being located at the point of intersection P of said intersectingfirst and second pivoting axes 19, 31.

The bearing means 23 is of the gimbal type, comprising an intermediatebearing element 33 which is pivotally supported by the first part 15 andwhich in its turn pivotally supports the second part 17, said point ofintersection P being located at the center point of the intermediatebearing element 33.

The laser source 25 is a semiconductor diode laser unit of a type knownper se that exhibits a far field radiation pattern 35 (see FIG. 3) in agenerally transverse cross-section of the radiation beam 27 of generallyoblong shape, with a major pattern axis 35L and an orthogonal minorpattern axis 35S. The semiconductor laser diode 25 is arranged such thatthe major pattern axis 35L is generally parallel to the second pivotalaxis 31 and the minor pattern axis 35S is generally parallel to thefirst pivotal axis 19.

The optical means of the second part 17 comprises an optical collimatingmeans in the form of a collimating lens 37 at the point of entry of thelaser beam 27 emitted by the diode laser 25 into the second part 17. Thecollimating lens 37 is wholly positioned within the generally oblong farfield pattern 35 of the semiconductor diode laser 25 in all operationalpivotal positions of the second part 17.

The pivoting optical device described so far is a swing arm device forsupporting an optical focusing unit 39 near its free end 41 forreading/recording information from/into the information surface 9 of theoptical disc 5 disposed on a rotating spindle 43 of the spindle motor11. The second part 17 is a rigid swing arm for pivotal scanningmovements about a swing axis which is the pivot axis 19, and for pivotalfocusing movements about a focusing axis, which is the second pivot axis31 that substantially orthogonally intersects the swing axis at P formoving the optical pickup unit 39 in substantially orthogonal scanningand focusing directions F and S, respectively, relative to theinformation surface 9 of the optical information disc 5. The majorpattern axis 35L (FIG. 3) of the far field pattern 35 is generallyparallel to the focusing axis 31 and the minor pattern axis 35 S of thefar field pattern is generally parallel to the swing axis 19.

The embodiment of the swing arm device shown in FIG. 1 is of a type inwhich the second part is a rigid swing arm structure which pivotallymoves as a whole about the swing axis 19 and the focusing axis 31. Tooenable these pivotal movements, magnetic scanning and focusing means areprovided, comprising the first part 15 which is of magneticallypermeable material and acts as a stator structure and a number ofmovable magnetic coils 45;47A,B which are provided at the free end 41 ofthe swing arm structure for scanning and focusing, respectively. Themovable magnetic scanning coil comprises a cylindrical scanning coil 45having a generally rectangular shape in cross-section and having acentral opening 49. The movable focusing coils are two substantiallyidentical cylindrical focusing coils 47A,B, respectively, having agenerally rectangular shape in cross-section. The scanning coil 45 hasbeen bonded with an outer side surface against the free end 41 of theswing arm structure 17 in a position in which its central axis isgenerally parallel to the scanning movements S of the swing armstructure, using suitable means such as adhesive means. Each focusingcoil 47A,B has been bonded at a portion of its outwardly facing axialend surface against an outer side surface of the scanning coil 45 whichis remote from the swing arm structure 17 by suitable bonding means suchas adhesive means, the two focusing coils 47A,B being disposed in themanner generally shown in FIG. 1. The first part 15 supports stationarymagnetic means comprising an elongate permanent magnet means 51 facingthe focusing coils 47A,B and spaced therefrom by an air gap. Themagnetically permeable stator or first part 15 has a stator part 53passing through the central opening 49 of the scanning coil 45 withclearance, the permanent magnet means 53 being magnetically polarized ina radial direction relative to the swing axis 19 of the swing armstructure or second part 17, the arrangement being such that asubstantially radially directed permanent magnetic field is establishedacross the air gaps which are present between the scanning coil 49 andthe stator part 53 and between the focusing coils 47A,B and the stator15, respectively. The stator 15 is rigidly associated with the spindlemotor 3.

The stator core 15 and supporting portions of the gimbal-type bearingmeans 23 are integrated into a combined unit. This combined unit is madefrom a suitable magnetically permeable material such as soft iron andcomprises a temporarily removable part, the part 53, to enable insertionof the scanning coil 45 into the central opening 49. The combined unitis provided with an interconnecting supporting beam part 55 carrying thebearing means 23 near its free end and may be comprised of a stack ofstator laminations which may be integrated with the motor stator of thespindle motor 3.

More detailed descriptions of swing arm devices of the general kindshown in FIG. 1 may be found in the previously mentioned patentapplication, filing nr. 02078880.8.

FIG. 1 illustrates that the second part 15 is generally U-shaped in planview at its free end 57, comprising two legs 59,61 and a connecting part63. Pivoting pins 65,67 pivotally support the intermediate part 33 inthe legs 59,61, respectively. In turn, the second part 15 is pivotallycarried by the intermediate bearing part 31 by two pivoting pins 69,71,respectively (FIG. 2). The diode laser is inserted in a matching openingin the connecting part 63 of the U-shaped end part of the second part 15in such a way that the active diode surface (not shown), which is housedinside a laser beam transparent protection cap 73 and emits the laserbeam 27, is situated at the point of intersection P of the swing axis 19and the focusing axis 31 of the second part 17.

FIG. 3 shows a projection of the collimating lens 37 as a circularshaded area, projected onto the local far field pattern shown as adifferently shaded area in a projection plane orthogonally passingthrough the plane of the collimating lens 37. The collimating lens 37remains within the boundaries of the far field pattern 35 in alloperational positions of the swing arm device 13 of FIG. 1 swingingabout the swing axis 19 and the focusing axis 31. The focusingamplitudes of swing arm devices for optical disc drives being muchsmaller than the swing amplitudes, a far field pattern of oblong shapeor generally unidirectionally extended shape appears to be highlysuitable in a pivoting optical device for optical disc drives.

FIG. 4 demonstrates that with bearings of the gimbal type suitable forthe invention the intermediate part need not be circular as in FIG. 1. Apivoting optical device 76, only part of which is schematically shown,comprises an intermediate part 75 of generally square shape, pivotallysupports a second part 77 by means of two pivot pins 79,81, and isprovided with two further pivot pins 83,85 for cooperation with a firstpart (not shown). It will be appreciated that intermediate parts of anysuitable shape may be used for the purposes of the invention.

To illustrate that other suitable bearing means may alternatively beused, depending on the nature of the application and the structure ofthe pivoting optical device, FIG. 5 schematically shows a detail of anoptical device 86 of a different kind, comprising a first part 87 and ahollow tubular second part 89. The bearing means is a spherical bearingarrangement 91 of swivel joint type comprising a partly sphericalmovable bearing part 93, omnidirectionally rotatably restrained in amatching outer stationary part 95 connected to a base plate 97. Thehollow tubular first part 89 penetrates the spherical part 93 so that anopening 99 in the first part is exposed on a side of the spherical partopposite to the side facing the major portion of the first part. A pointradiation source is supported on a stationary mount 101 facing theopening 99 and penetrating it such that the active part of the pointradiation source is located in the point of intersection Q of twoorthogonal pivot axes 103 and 105 of the bearing means 91.

While several embodiments of an optical disc device according to theinvention have been described, it will be appreciated by persons skilledin the art that the invention is not limited by what has beenparticularly described and shown above. Many modifications are possiblewithout departing from the inventive concepts herein, all comprising themain feature of the invention, which is that in a pivoting opticaldevice a laser source is located in an optical laser beam path in thegeneral longitudinal direction of a second part, and bearing meanspresent an open center region so as to allow a laser beam to pass from alaser source to the second pivotally movable part. Different designs ofbearing means may be used or conceived, for example comprising flexiblepivot elements instead of or in addition to mutually movable pivotelements.

1. A pivoting optical device, comprising: a first part, a second partprovided with optical means and pivotally movable relative to the firstpart about a first pivot axis, said optical means defining an opticallaser beam path in the general longitudinal direction of the secondpart, bearing means comprising the first pivot axis, a point lasersource fixedly connected to the first part for providing a laser beam inthe general direction of said second part, wherein: the laser source islocated in said optical laser beam path in the general longitudinaldirection of the second part, and the bearing means presents an opencenter region so as to allow a laser beam to pass from the laser sourceto the second pivotally movable part.
 2. A pivoting optical deviceaccording to claim 1, wherein the second part is also pivotally movablerelative to the first part about a second pivot axis substantiallyorthogonally intersecting the first pivot axis at a point ofintersection, the laser source being located at the point ofintersection of said intersecting first and second pivoting axes
 3. Apivoting optical device according to claim 2, wherein the bearing meansis of the gimbal type, comprising an intermediate bearing element whichis pivotally supported by the first part and which in its turn pivotallysupports the second part, said point of intersection being located atthe center of the intermediate bearing element.
 4. A pivoting opticaldevice according to claim 2, wherein: the laser source is asemiconductor diode laser unit of a type known per se exhibiting a farfield radiation pattern in a generally transverse cross-section of theradiation beam of generally oblong shape, with a major pattern axis andan orthogonal minor pattern axis, and wherein the semiconductor laserdiode is arranged such that the major pattern axis is generally parallelto one of the first and second axes, and the minor pattern axis isgenerally parallel to the other one of the first and second axes.
 5. Apivoting optical device according to claim 2, wherein said optical meansof the second part comprises optical collimating means at the point ofentry of a radiation beam emitted by the laser source into the secondpart.
 6. A pivoting optical device according to claim 4, wherein thecollimating means is wholly positioned within the generally oblong farfield pattern of the semiconductor diode laser in all operationalpivotal positions of the second part.
 7. A pivoting optical deviceaccording to claim 4, wherein the pivoting optical device is a swing armdevice for supporting an optical focusing unit near its free end forreading/recording information from/into an information surface of anoptical disc disposed in an optical disc apparatus, the second partbeing a rigid swing arm for performing pivotal scanning movements abouta swing axis and for performing pivotal focusing movements about afocusing axis that substantially orthogonally intersects the swing axisso as to move an optical pickup unit in mutually substantiallyorthogonal scanning and focusing directions, respectively, relative tothe information surface of the optical information disc, and wherein:the major pattern axis of the far field pattern is generally parallel tothe focusing axis, and the minor pattern axis of the far field patternis generally parallel to the swing axis.